The present invention relates to a fluid pressure control device for a vehicle braking system, and more particularly to a fluid pressure control valve unit of the inertia-controlled type which is adapted to control the braking pressure applied to rear wheel brake cylinders from a master cylinder in accordance with the rate of deceleration of the vehicle.
In FIG. 1 there is illustrated one of such conventional control valve units as described above, in which a housing assembly 5 is provided with an inlet port 2 in connection to a tandem master cylinder 1 and an outlet port 4 in connection to rear wheel brake cylinders 3. Assembled within a single bore 6 of housing assembly 5 are a spring loaded stepped piston 7, an inertia-controlled valve assembly 10 including an inertia-controlled ball 9, and a spring loaded control plunger 11 for control of the piston 7. Furthermore, a pair of partition members 13 and 14 are assembled within the single bore 6 of housing assembly 5 in such a way to provide a space 12 between partition members 13, 14 and to subdivide the interior of housing assembly 5 into first and second chambers 15 and 16. Thus, one end portion of stepped piston 7 extends into the space 12 and is slidably supported from the partition member 13. The control plunger is also slidably disposed within an axial bore of partition member 14. In such arrangement, it is required to provide communication passages 17, 17 through the peripheral wall of housing assembly 5 so as to communicate the inlet port 2 to the first and second chambers 15 and 16 respectively. This results in large of the housing assembly in its size and weight.